5'-3' exonuclease
SMART accession number:SM00475
Description: -
Interpro abstract (IPR002421):

This entry represents flap endonucleases from eukaryotes, bacteria, viruses and archaea. Flap endonucleases (FENs) catalyse the exonucleolytic hydrolysis of blunt-ended duplex DNA substrates and the endonucleolytic cleavage of 5'-bifurcated nucleic acids at the junction formed between single and double-stranded DNA [ (PUBMED:17559871) ].

In prokaryotes, the essential FEN reaction can be performed by the N-terminal 5'-3' exonuclease domain present on DNA polymerase I. Some eubacteria, however, possess a second gene encoding a 5'-3' exonuclease domain [ (PUBMED:19000038) (PUBMED:23821668) ]. Two distinct classes of these independent bacterial FENs exist: Xni (ExoIXI) from Escherichia coli and SaFEN (Staphylococcus aureus FEN). SaFEN has both FEN and 5'-3' exonuclease activities. Xni (ExoIX) was previously identified as a 3'-5' exonuclease and named exonuclease IX (exonuclease 9) [ (PUBMED:9592142) (PUBMED:9840179) ] but subsequently found to possess flap endonuclease activity, but not exonuclease activity [ (PUBMED:17567612) (PUBMED:19000038) (PUBMED:23821668) ].

Archaea, eukaryotes, bacteriophages and some viruses encode a separate FEN enzyme but lack FEN domains on their DNA polymerases [ (PUBMED:23821668) ]. Escherichia phage T5 encodes the flap endonuclease D15, which catalyzes both the 5'-exonucleolytic and structure-specific endonucleolytic hydrolysis of DNA branched nucleic acid molecules [ (PUBMED:9874768) (PUBMED:15077103) (PUBMED:10364212) ]. In bacteriophage T4, disruption of the rnh gene (which encodes a FEN, known historically as T4 RNase H) results in slower, less accurate DNA replication. Bacteriophage T4 has both 5' nuclease and flap endonuclease activities [ (PUBMED:17693399) ].

GO function:DNA binding (GO:0003677)
Family alignment:
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There are 27001 53EXOc domains in 27001 proteins in SMART's nrdb database.

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